Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
In home: 48 to 96 hours
Locations and reports
Radon Levels in Alameda County, California
EPA puts Alameda County in Zone 2, its middle radon zone, and most reported tests there come back low, though 6.7% of 478 (2008 to 2017, laboratory totals) reached 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
6.7%
3.6 pts below CA
- Alameda
- 6.7%
- California
- 10.3%
478 tests, 2008 to 2017
Median result
0.7pCi/L
Below action level
- Alameda
- 0.7 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
478
4th of 33 by tests
- Alameda
- 478
- Los Angeles
- 2,363
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Rank in California
25 of 33
Middle half
- Alameda
- 6.7%
- El Dorado
- 30.3%
By share, of 33 with 30+ tests
Read a result for Alameda County
Starts at Alameda County's median, 0.7 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 0.7 pCi/L
Below 2 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Alameda County's median reported result, 2008 to 2017.
The data
Alameda County, At a glance
Alameda County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Alameda County is a
USGS geologic potential: Moderate across 98% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Alameda County, 2008 to 2017, laboratory
Under 2 pCi/L: 84%2 to 4 pCi/L: 9%4 pCi/L and above: 7%
Of 478 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 403 | 84.3% |
| 2 to 4 pCi/L | 43 | 9.0% |
| 4 pCi/L and above | 32 | 6.7% |
What these figures count
These are the 478 tests reported to CDC for Alameda County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.
Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Alameda County, Compared
Alameda County radon figures, compared
Calculated by Radon411Alameda County reports fewer high tests than California overall. 6.7% of its 478 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 3.6 points below the 10.3% pooled from 56 California counties.
Ordered from highest share down, it comes 25th of 33 California counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; Alameda County sits 29.0 points below it.
Next door, the shares run from 8.8% in Contra Costa County to 14.9% in San Joaquin County. The reported tests do not follow EPA's Zone 2 label for Alameda County (predicted average between 2 and 4 pCi/L): 6.7% of them reached 4 pCi/L, fewer than that label suggests.
Half the tests came in under 0.7 pCi/L and half over it; the single highest reached 159.8 pCi/L. The rest split 84.3% under 2 pCi/L and 9.0% from 2 to 4 (California: 76.8% and 12.9%).
CDC's ten-year totals for Alameda County went from 491 tests (2005 to 2014) to 478 (2008 to 2017), the share going from 7.3% to 6.7%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Alameda County, Geology
The ground under Alameda County
PredictedMost of the ground under Alameda County is one class on USGS's geologic map: 98.5% of its land is moderate radon potential, with 0.8% low. 98.5% of it lies in the area the map calls Southern Coast Ranges, to which USGS gives a radon index of 9, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Southern Coast Ranges | Metamorphosed marine sedimentary rocks, ultramafic rocks, Triasic metamorphic rocks, Mesozoic granitic rocks, and a series of fault-bounded linear basins in which Teriary marine and continental sedimentary rocks were deposited. | Moderate | 9 | 98.5% |
| Great Valley | Quaternary alluvial gravel, sand, silt, clay. | Low | 8 | 0.8% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Alameda County beside the ground around it
Across California 0.1% of the land is rated high; none of Alameda County's is. Of the 4 counties that border it, 1 has more moderate-potential ground, Santa Clara County the most at 99.9%.
The map rates the ground, not the air in any home.
Local help
Alameda County, Local resources
Radon testing and mitigation in Alameda County
- California Indoor Radon ProgramCalifornia Indoor Radon Program, run by California Department of Public Health, licenses or certifies radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in California.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Discounted test kits can be purchased through our partner laboratory, Alpha Energy, for $14.95.
- Compare kits
- Professionals in California4 professionals are listed in California.
What California's program says
- Phone
- 1-800-745-7236
- Radonprogram@cdph.ca.gov
- Licensing of radon professionals
The Radon Program certifies all radon service providers operating in California.
What it means
Alameda County, Questions
Questions about radon in Alameda County
Are radon levels high in Alameda County?
Over the 2008 to 2017 laboratory totals, 6.7% of the radon tests reported to CDC for Alameda County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.7 pCi/L. Of 33 California counties with 30 or more tests for the same period, 24 reported a higher share; pooled, the state comes to 10.3%.
Which counties border Alameda County?
Alameda County borders 4 counties: Contra Costa County, Santa Clara County, San Joaquin County and Stanislaus County.
Products
Alameda County, Products
Testing a home in Alameda County
In Alameda County, 6.7% of 478 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 10.3% pooled across California. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Alameda County; a long-term test tells the year-round average.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Monitor
Hello Radon C battery radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Alameda County, Bordering counties
Counties bordering Alameda County
Calculated by Radon411- Radon levels in San Joaquin CountyEPA zone 3
14.9%at or above 4 pCi/L
Median 1.4 pCi/L · 74 tests · 8.2 points above Alameda County
- Radon levels in Stanislaus CountyEPA zone 3
11.1%at or above 4 pCi/L
Median 1.4 pCi/L · 27 tests · 4.4 points above Alameda County
- Radon levels in Santa Clara CountyEPA zone 2
9.2%at or above 4 pCi/L
Median 0.9 pCi/L · 793 tests · 2.5 points above Alameda County
- Radon levels in Contra Costa CountyEPA zone 2
8.8%at or above 4 pCi/L
Median 0.9 pCi/L · 285 tests · 2.1 points above Alameda County
Alameda County, Cities and towns
Cities and towns in Alameda County
About 1,636,630 people live in Alameda County by the Census Bureau's estimate for July 1, 2025, 43,859 fewer than in 2020 (−2.6%). Packed into its land, that is 2,219 people per square mile. Its largest town, Oakland, has 440,838 residents, 26.9% of the total. Together its 14 incorporated places hold 91.3% of those residents; the other 8.7% live outside any of them. CDC's 478 reported tests for 2008 to 2017 work out to 0.3 per 1,000 residents (2025 estimate), close to California's 0.2.
From Oakland to Piedmont, CDC publishes no figure by town: each reads Alameda County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Oakland | 440,838 | −0.1% | 26.9% |
| Fremont | 226,442 | −1.7% | 13.8% |
| Hayward | 157,113 | −3.4% | 9.6% |
| Berkeley | 121,911 | −1.8% | 7.4% |
| San Leandro | 85,353 | −5.9% | 5.2% |
| Livermore | 83,457 | −5.0% | 5.1% |
| Alameda | 76,876 | −1.6% | 4.7% |
| Pleasanton | 74,556 | −6.4% | 4.6% |
| Dublin | 71,602 | −0.8% | 4.4% |
| Union City | 65,282 | −6.6% | 4.0% |
| Newark | 47,895 | +0.8% | 2.9% |
| Albany | 19,195 | −5.0% | 1.2% |
- Emeryville
- Piedmont
14 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).
Alameda County, Homes
Homes in Alameda County
Fewer than six in ten of Alameda County's 630,726 homes are detached houses (51%, against 57% across California); the rest are attached, in shared buildings or mobile. Half of its homes were built before 1969, close to California's 1976: 39% date from before 1960 and 14% from 2000 or later. 54% of occupied homes are lived in by their owner (California: 56%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Alameda County | California |
|---|---|---|
| Housing units | 630,726 | 14,532,683 |
| Detached houses | 51% | 57% |
| In buildings of 5 or more | 29% | 24% |
| Mobile homes | 1% | 4% |
| Built before 1960 | 39% | 27% |
| Built since 2000 | 14% | 18% |
| Middle year built | 1969 | 1976 |
| Owner-occupied | 54% | 56% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.